3.

20 10 150 obtuse triangle

32 67 8 1 acute triangle

4.

( 1)④⑤⑥

(2)①②④

(3)①②④⑤

5.

There are 2 acute triangles, 6 right triangles, 3 obtuse triangles and 5 isosceles triangles.

6.

Bottom height

7.

( 1)(6,5) (2,3) ( 1 1,2)

(2) (5,0)

Page 85

First, calculation.

1.

9000 72000 20000

140004800? ? 1000

2.

13756 14520 3 1200

3.

=(37+63)+ 138

= 100+ 138?

=238? ?

=2x25x 17

=50x 17

=850

630 lbs (18x5)

=630÷90

=7

=243-(29+7 1)

=243- 100

= 143

= 37 times (56+44)

=37x 100

=3700

=22x( 188-88)

=22x 100

=2200

Page 86

Third, choose the right answer.

1.□ □√ □

2.□ □ □√

3.□√□ □

4.□ □√□

5.□ □√□

6.□√ □ □

Fourth, draw a picture.

1. Hint: The painting method is not unique.

Page 87

Five,

1.

100

1000

10000

9876 x9+ 1 1 1 16 = 100000

2.

100

1 100

1 1 100

12345 x9-5 = 1 1 1 100

Six,

300 yuan

8 boxes

12 yuan/kg

108m

6 points

90 km/h

Seven,

1.

( 1)

(26- 18)x5

=8x5

= 40 (yuan)

(2)

( 142-26x3)÷2

=( 142-78)÷2

=64÷2

= 32 (yuan)

2.

(85+ 1 10)x5

= 195x5

=975 km

Page 88

5.

(1)4 hours and 30 minutes

(2) 5 pm

6.

Excellent: 8 people

Good: Five people.

8-5=3 people

7.

20 ÷ 4 = 5 (Ben)

20-5 = 15 (Ben)

A: There are five books left, and 15 books have been borrowed.